The invention relates to grafted copolymers comprising at least three sequences of distinct chemical nature, among which one or more sequence(s) for anchoring on solid particles, one or more sequence(s) of hydrophobic character and one or more sequence(s) of hydrophilic character.
The invention also concerns their process of preparation, the compositions containing them, their use as dispersing agent, stabilizer of solid particles and/or emulsifier in an aqueous and/or organic medium, as well as their use for the preparation of pigmentary dispersions in an aqueous and/or organic medium.
At the end of their process of manufacture, the solid particles used in the ink and paint industry, essentially pigments and fillers, are in the form of aggregates or agglomerates. Their incorporation in a liquid in order to obtain a stable suspension therefore necessitates a prior step of dispersion, step during which these assemblies are dissociated into elementary particles under the effect of considerable mechanical stresses.
However, the action of these mechanical forces could not be efficient in the absence of a dispersing agent.
These copolymers, employed in solution by adsorption on the surface of the solid, or by coating of the particle before incorporation thereof in the liquid, intervene at each step of the dispersion.
Firstly, they ensure a good wetting of the particle by the continuous phase, by replacing the film of air surrounding the surface of the solid by molecules of liquid. They then substantially improve the output of the dissolvent/grinder during the phase of disagglomeration of the associates. Finally, these dispersion agents, adsorbed on the surface of the solid, constitute a layer of solvated polymer, at the origin of steric forces of repulsion, and, in the case of polyelectrolytes in aqueous medium, of electrostatic forces of repulsion, which oppose the attractive Van de Waals forces, thus ensuring the stability of the dispersion.
In order to be efficient, a copolymer which may be used as a dispersant must therefore comprise a sequence of anchoring, presenting a good affinity for the surface of the particles, as well as one or more sequence(s) compatible with the continuous phase in which these solids are incorporated.
In the absence of one of these constituents, or in the case of desorption of the dispersant, the system flocculates, a phenomenon which shows itself by the reagglomeration of the particles, and an increase in viscosity of the dispersion. In the particular case of a paint, a poor dispersion of the pigments within the binding agent is translated by considerable colorimetric divergences and loss of brillance on the final film.
In order to overcome these problems, dispersion agents have been proposed, which make it possible to formulate paints specifically in aqueous medium (EP 018 099) or in organic medium (U.S. Pat. No. 4 032 698; GB 1 393 401 and 1 393 402). However, these products offer only a partial solution, insofar as the mixture of different pigments, inorganic and organic, or interactions between the dispersant and the continuous phase, as may be the case in lacquers, bring about a loss of stability of the suspension.
The synthesis of new additives, containing several sequences, based on the use of polyisocyanates, as described in Patents U.S. Pat. No. 4,647,647 or EP 0 520 586, makes it possible to overcome these difficulties. Nonetheless, the use of polyisocyanates, molecules presenting a high toxicity and poorly defined functionality, leads to obtaining a product constituted by a mixture of various structures, of which the properties of adsorption and of dispersion are not optimal. In addition, this process prevents the presence in the copolymer of polar functions containing a reactive hydrogen atom, chemical functions appreciated when using in an aqueous medium or for promoting the compatibility with the resins.
Furthermore, monografted copolymers, obtained by the xe2x80x9cmacromonomerxe2x80x9d technique and/or grafting of telomers of polyether type on a preformed chain constituted by one or more unsaturated ethylene monomers and comprising nitrogenous moeities, form the subject matter of Patent EP 0 311 157.
The copolymers of the present invention contain a sequence allowing them to be anchored on the solid particles, particularly pigments and fillers, as well as at least 2 sequences of respectively hydrophilic and hydrophobic character, allowing use thereof in the compositions in aqueous and/or organic medium. The presence of a sequence insoluble in selective medium surprisingly increases the quantity of dispersant adsorbed on the surface of the particles, thus avoiding the phenomenon of flocculation during the mixture of different pigments.
On the other hand, the plurality of chemical functions within the same copolymer, as well as the possibility of formulating pigmentary concentrates without elongation resin, improve compatibility with the resins, thus allowing the formulation of paints from a wide range of binding agents.
Moreover, the process of synthesis makes it possible to obtain products of homogeneous structure, whose performances are not limited by the presence of contaminants.
The invention therefore has for its object a grafted copolymer comprising at least three sequences of distinct chemical nature, among which one or more sequence(s) for anchoring on the solid particles, one or more sequence(s) of hydrophobic character and one or more sequence(s) of hydrophilic character, constituted by:
1) 1 to 80% by mass, preferably 5 to 40% by mass, of one or more sequence(s) for anchoring on the solid particles, constituted by a straight or branched hydrocarbon chain, cycloalkyl or aromatic, comprising basic nitrogenous groups of type: heterocyclic, xe2x80x94NH2, xe2x80x94NH, xe2x80x94NHR, xe2x80x94NR2, xe2x80x94CONH2, xe2x80x94CONHR, xe2x80x94CONR2 (where R is an alkyl radical (C1-C6) optionally substituted by one or more groups xe2x80x94OH, xe2x80x94COOxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94SO3H), which may comprise xe2x80x94COOxe2x80x94 groups, and whose molar mass is included between 150 and 10000, preferably between 300 and 3000, the mass content of basic nitrogenous monomers in the anchoring chain being 5% minimum and preferably 30%, and
2) 10 to 90% by mass, preferably 25 to 80% by mass, of one or more sequence(s) of hydrophobic character, constituted by a straight or branched hydrocarbon chain, cycloalkyl or aromatic, which may comprise groups xe2x80x94COOxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94F, xe2x80x94Si(ORxe2x80x2)n(Rxe2x80x3)2-nxe2x80x94 (where Rxe2x80x2 and Rxe2x80x3 represent similar or different alkyl or aryl radicals (C1-C10) and n=0 to 2), formed by monomer units whose parameter of solubility is less than or equal to 21.5 Jxc2xd/cm{fraction (3/2)}, preferably less than 19 Jxc2xd/cm{fraction (3/2)}, and whose molar mass is included between 250 and 10000, preferably between 500 and 3500, and
3) 10 to 90% by mass, preferably 15 to 70% by mass, of one or more sequence(s) of hydrophilic character, constituted by a straight or branched hydrocarbon chain comprising groups xe2x80x94Oxe2x80x94, xe2x80x94OH, xe2x80x94NCOxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94COOH, xe2x80x94CONH2, xe2x80x94CONHRxe2x80x2xe2x80x3 (where Rxe2x80x2xe2x80x3 is an alkyl radical (C1-C3)), xe2x80x94NHxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO3H, formed by monomer units whose parameter of solubility is greater than 22 Jxc2xd/cm{fraction (3/2)}, preferably greater than 22.5 Jxc2xdcm{fraction (3/2)}, and whose molar mass is included between 250 and 10000, preferably between 300 and 3000.
It will be noted that there advantageously exist three different ways of combining the three types of sequences: anchoring, hydrophobic and hydrophilic. The grafted copolymers according to the invention may therefore present the following structures alternately:
principal anchoring chain+at least 2 respectively hydrophilic and hydrophobic grafts
principal hydrophobic chain+at least 2 respectively hydrophilic and anchoring grafts
principal hydrophilic chain+at least 2 respectively hydrophobic and anchoring grafts.
The grafted copolymers comprising a principal anchoring chain and at least 2 respectively hydrophilic and hydrophobic grafts are preferred compounds according to the invention.
According to a preferred aspect, the invention concerns a grafted copolymer as defined hereinabove comprising at least three sequences of distinct chemical nature, in which the principal chain is a sequence of anchoring on the solid particles constituted by a straight or branched hydrocarbon chain, cycloalkyl or aromatic, comprising basic nitrogenous groups of type: heterocyclic, xe2x80x94NH2, xe2x80x94NHxe2x80x94, xe2x80x94NHR, xe2x80x94NR2, xe2x80x94CONH2, xe2x80x94CONHR, xe2x80x94CONR2 (where R is an alkyl radical (C1-C6) optionally substituted by one or more groups xe2x80x94OH, xe2x80x94COOxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94SO3H) which may comprise groups xe2x80x94COOxe2x80x94, and whose molar mass is included between 150 and 10000, preferably between 300 and 3000, the mass content in basic nitrogenous monomers in the anchoring chain being 5% minimum and preferably 30%.
The invention advantageously also concerns a grafted copolymer as defined hereinabove, in which the principal chain is a sequence of hydrophobic character constituted by a straight or branched hydrocarbon chain, cycloalkyl or aromatic, which may comprise groups xe2x80x94COOxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94F, xe2x80x94Si(ORxe2x80x2)n(Rxe2x80x3)2-nxe2x80x94 (where Rxe2x80x2 and Rxe2x80x3 represent similar or different, alkyl or aryl radicals (C1-C10) and n=0 to 2), formed by monomer units of which the parameter of solubility is less than or equal to 21.5 Jxc2xd/cm{fraction (3/2)}, preferably less than 19 Jxc2xd/cm{fraction (3/2)}, and whose molar mass is included between 250 and 10000, preferably between 500 and 3500.
Other preferred grafted copolymers are products as defined hereinabove, in which the principal chain is a sequence of hydrophilic character, constituted by a straight or branched hydrocarbon chain, comprising groups xe2x80x94Oxe2x80x94, xe2x80x94OH, xe2x80x94NCOxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94COOH, xe2x80x94CONH2, xe2x80x94CONHRxe2x80x2xe2x80x3 (where Rxe2x80x2xe2x80x3 is an alkyl radical (C1-C3)), xe2x80x94SO3H, formed by monomer units of which the parameter of solubility is greater than 22 Jxc2xdcm{fraction (3/2)}, and of which the molar mass is included between 250 and 10000, preferably between 300 and 3000.
The parameters of solubility expressed in Jxc2xd/cm{fraction (3/2)} were calculated by the Hoftyzer-Van Krevelen method of incrementation or measured experimentally (case of polydimethyl-siloxane). The molar volumes necessary for calculating the parameters of solubility are calculated from the Feedor data. These means of calculation and experimental values are set forth in the work by D. W. VAN KREVELEN xe2x80x9cProperties of polymers. Their correlation with chemical structure; their numerical estimation and prediction from additive group contributionsxe2x80x9d, Third edition, Elsevier 1990, pages 189-225.
The invention also concerns said copolymer in the form of one of its salts, obtained by quaternization or neutralization of the basic functions.
The invention also relates to the processes for preparing the grafted copolymers defined hereinabove.
The synthesis of the grafted copolymers according to the invention is based on the use of the xe2x80x9cmacromonomerxe2x80x9d technique and/or the grafting of functionalized telomers on a preformed grafted or straight chain.
Thus, these dispersants may be prepared by radical-like copolymerization of one or more hydrophilic macromonomer(s) and of one or more hydrophobic macromonomer(s) with one or more nitrogenous comonomer(s) and optionally with one or more unsaturated ethylene comonomer(s) and/or reactive unsaturated ethylene comonomer(s).
These syntheses are effected under inert atmosphere in the presence of a solvent or an appropriate mixture of solvents, i.e. in which the reagents, macromonomers, comonomers are totally soluble and the final products are totally or at least partially soluble. These solvents will in particular be selected from the aromatic hydrocarbons such as toluene or xylene; ethers such as dioxane or tetrahydrofuran, ketones such as acetone or methylethylketone, esters such as ethyl acetate or butyl acetate. Dioxane or tetrahydrofuran will preferably be used in the preparation of the grafted copolymers.
Synthesis begins by the preparation of the macromonomers, by telomerization then fixation of a double bond at the end of chain, followed by the copolymerization of said macromonomers with the comonomers.
The grafted copolymers according to the invention may also be prepared by fixing one or more functionalized molecules, one of the two types of hydrophilic or hydrophobic grafts, or even the two types of grafts, on a polymer preformed with the aid of reactive monomers, this chain already being able to contain one or more hydrophilic or hydrophobic graft(s) incorporated by radical-like method. In that case, the course of the reaction imposes the use of at least two distinct reactors, the first serving for preparing the principal chain, the second intended for preparing the telomer.
Grafting of these side chains on the preformed polymer may then be carried out by adding the contents of the reactor or reactors containing the telomers to the first. It may be advantageous to effect this addition in several steps in order to adjust the properties of the final copolymer as best possible.
The invention also relates to compositions containing one or more grafted copolymer(s) as defined hereinabove, at least one pigment and/or one filler and/or a fibrous solid, and, optionally, an organic solvent and/or water.
The invention also has for an object a pigment or a filler or a coated fibrous solid from compositions containing one or more grafted copolymer(s) as defined hereinabove.
Finally, the invention concerns the use of said copolymer(s) as dispersing agents, stabilizers of solid particles or emulsifiers in an aqueous and/or organic medium, their use for preparing pigmentary dispersions in aqueous and/or organic medium and the paints and inks containing them.
The grafted copolymers according to the invention present, distributed along their sequence of anchoring, basic nitrogenous groups disposed in statistic manner and chosen for their affinity with the surface of numerous pigments and fillers, both organic and inorganic.
Said basic groups may be defined by their pKa, included between 2 and 14, preferably between 5 and 14, in particular between 5 and 12. The measurements of pKa are made at 25xc2x0 C. in water at a molar concentration of 0.01.
According to one of its aspects, the invention therefore concerns a grafted copolyer as defined hereinabove in which the anchoring sequence(s) comprises or comprise basic nitrogenous groups introduced from one or more compounds selected for example from:
a) the vinylpyridines, such as 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine or 2-methyl-5-vinylpyridine,
vinylimidazole, 2-methyl-N-vinylimidazole, vinyl-carbazole, N-vinylpyrrolidone, 3-methyl-N-vinlpyrazole, 4-methyl-5-vinylthiazole, N-vinylcaprolactam, ethylimidazolidone methacrylate,
the (meth)acrylamides such as (meth)acrylamide, N-methylacrylamide, N-isopropylacrylamide and N,N-dimethylacrylamide,
N-methylol(meth)acrylamide, N,N-dimethylol(meth)acryl-amide, 2-acrylamido-2-methyl-1-propanesulfonic acid, diacetone acrylamide, methyl-2-acrylamido-2-methoxyacetate, N-tris-(hydroxymethyl)methylacrylamide,
the aminoalkyl(meth)acrylates of following formula: 
where R1 is an atom of hydrogen or an alkyl radical (C1-C4); R2 and R3, identical or different, each represent an alkyl radical (C1-C6), n=0 to 6, said nitrogenous groups being in this first case introduced by radical-like copolymerization of one or more unsaturated ethylene monomer(s) mentioned hereinabove, and
b) N-N-diethyl-1,4-butanediamine, 1-(2-aminoethyl)-piperazine, 2-(1-pyrrolidyl)-ethylamine, 4-amino-2-methoxy-pyrimidine, 2-dimethylamino-ethanol, 1-(2-hydroxyethyl)-piperazine, 4-(2-hydroxyethyl)-morpholine, 2-mercapto-pyrimidine, 2-mercaptobenzimidazole, N,N-dimethyl-1,3-propanediamine, 4-(2-aminoethyl)-pyridine, N-N-diallyl-melamine, 3-amino-1,2,4-triazole, 1-(3-aminopropyl)-imidazole, 4-(2-hydroxyethyl)-pyridine, 1-(2-hydroxyethyl-imidazole, 3-mercapto-1,2,4-triazole, said nitrogenous groups being in this second case fixed on a straight or grafted copolymer, putting to good use the reactive functions introduced along the preformed chain.
Among compounds a), use will preferably be made of the monomers of vinylpyridine, vinylimidazole, (meth)acrylamide, N,N-dimethylacrylamide and 2-dimethylaminoethyl methacrylate type.
Compounds b) mentioned hereinabove are preferably grafted directly on the copolymer from reactive chemical functions incorporated by radical-like copolymerization of one or more reactive unsaturated ethylene monomer(s) containing one or more groups comprising at least one atom of hydrogen reactive with respect to functions such as for example the epoxy group, selected from xe2x80x94OH, xe2x80x94SH, xe2x80x94COOH, xe2x80x94NH2, xe2x80x94NHR (where R is an alkyl radical possessing from 1 to 3 carbon atoms).
The following may be used for example:
hydroxylated compounds: 2-hydroxyethyl (meth)acrylate, 2- or 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)-acrylate,
carboxylated compounds: (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, maleic anhydride,
monomers bearing an epoxy function: glycidyl meth-acrylate.
Monomers bearing hydroxy and epoxy functions will preferably be used, and more particularly hydroxyethyl (meth)-acrylates, hydroxypropyl (meth)acrylates and glycidyl meth-acrylate.
The proportion of the reactive monomers contained in the copolymer lies between 0 and 80% by mass, preferably between 0 and 40% by mass.
It is often advantageous likewise to copolymerize one or more neutral unsaturated ethylene monomer(s) with the nitrogenous monomer(s) a) mentioned hereinabove and/or the reactive monomer(s) allowing grafting of the compounds b) mentioned above.
In fact, these monomers, although they do not influence the dispersing and stabilizing capacities of the copolymer directly, make it possible favourably to modify certain of its properties, such as for example its vitreous transition temperature, its stability or its mechanical properties.
These monomers will for example be acrylic or methacrylic acid esters, vinyl, styrene or alkylstyrene esters.
The content of neutral unsaturated ethylene monomers in the final copolymer may vary from 0 to 76% by mass, and in particular from 0 to 28% by mass.
The unsaturated ethylene monomers introducing the compounds a), the reactive unsaturated ethylene monomers used for grafting the compounds b) and the neutral unsatured ethylene monomers described hereinabove as well as the hydrophilic and hydrophobic macromonomers are copolymerized by radical-like method from conventionally used primers, for example organic peroxides, redox systems, or preferably azo compounds.
The sequence(s) of hydrophobic character are chosen so that their properties of solubility are complementary of those of the sequence(s) of hydrophilic character mentioned hereinafter, in order to give the bigrafted copolymer its character of universal dispersant with respect to solvents and binding agents.
The organosoluble polymers formed by monomer units whose parameter of solubility is less than or equal to 21.5 Jxc2xd/cm{fraction (3/2)}, preferably less than 19 Jxc2xd/cm{fraction (3/2)}, constitute these sequences of hydrophobic character and make it possible to disperse the particles in a polar medium. The incorporation of this (these) sequence(s) or graft(s) in the copolymer may be effected by copolymerizing by the radical-like method one or more organosoluble macromonomer(s) with one or more unsaturated ethylene comonomer(s) mentioned above in the description of the anchoring sequence, namely one or more nitrogenous ethylene monomer(s), optionally one or more neutral unsaturated ethylene monomer(s) and at least one macromonomer of hydrophilic character described hereinbelow (from the primers usually used, for example organic peroxides, redox systems or preferably azo compounds), and will lead to the formation of a bigrafted copolymer.
These grafts of hydrophobic character may also be fixed by grafting on a straight or branched copolymer constituted by one or more unsaturated ethylene monomer(s) mentioned above in the description of the anchoring sequence, namely one or more monomer(s) a) and/or one or more reactive unsaturated ethylene monomers(s) used to graft the compounds b) on the copolymer and/or one or more neutral unsaturated ethylene monomer(s) and/or one or more macromonomer(s) of hydrophilic character described hereinbelow and/or of hydrophobic character, from one or more telomer(s) of hydrophobic character.
The telomers of hydrophobic character may be grafted directly on the copolymer with the aid of the reactive groups in accordance with the process described hereinabove for the anchoring sequence.
According to the invention, the monomer units constituting the macromonomers and telomers used for preparing the sequence(s) of hydrophobic character will for example be introduced from the following compounds:
(meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)-acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)-acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, behenyl (meth)acrylate, 3-(trimethoxysilyl)-propyl (meth)acrylate,
vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl sorbate, vinyl hexanoate, vinyl ethyl-hexanoate, vinyl laurate, vinyl stearate,
styrene and alkystyrenes such as xcex1-methylstyrene, vinyl-toluene, tertiobutylstyrene,
dienes such as butadiene, isoprene, which may be hydrogenated after polymerization,
alkylenes such as ethylene, propylene,
siloxans such as dimethylsiloxan, diphenylsiloxan, methyl-phenylsiloxan,
fluorinated compounds such as trifluoroethyl (meth)acrylate, pentafluoropropyl (meth)acrylate, heptafluorobutyl (meth)acrylate, octafluoropentyl (meth)acrylate, pentadecafluorooctyl (meth)acrylate, eicosafluoroundecyl (meth)acrylate, vinyl fluoride, tetrafluoroethylene.
The products of polycondensation, polyesters or polyamides, such as those prepared from either diacids and diols with long alkyl chains, or from hydroxyacids with long alkyl chains (for the polyesters), or from either diacids and diamines with long alkyl chains, or aminoacids with long alkyl chains (for the polyamides) may also constitute the telomers and macromonomers used.
Preferably, the grafted copolymers according to the invention will be prepared by radical-like copolymerization from one or more macromonomer(s), of which the constituent units are preferably chosen from the (meth)acrylic acid esters or vinyl esters comprising at least 8 carbon atoms, as well as the styrenics and alkylstyrenics such as styrene and tertio-butylstyrene and the fluorinated monomers, in particular tri-fluoroethyl methacrylate, and synthesized by telomerization from a chain transfer agent, then condensation on a (meth)-acrylic, vinylic or allylic, preferably (meth)acrylic monomer.
The molar mass of the hydrophobic grafts obtained by this technique is included between 250 and 10000 and will advantageously be included between 500 and 3500.
On the other hand, the content of hydrophobic grafts in the final bigrafted copolymer by mass is included between 10 and 90% and preferably between 25 and 80%.
The sequence(s) of hydrophilic character, distributed statistically along the principal chain of the copolymer, are at the origin of the solubility of the copolymers in water. It is these sequences which stabilize the dispersions of particles in aqueous medium.
The parameter of solubility of the monomer units constituting these grafts is greater than or equal to 22 Jxc2xd/cm{fraction (3/2)}, preferably greater than 22.5 Jxc2xd/cm{fraction (3/2)}.
The introduction of these side chains in the copolymer may be effected by using one or more macromonomer(s) of hydrophilic character. A macromonomer of this type is composed of a hydro-soluble polymer terminated at one of its ends by a group which is polymerizable in radical manner. This group may for example be of the (meth)acrylic, vinylic or allylic, preferably (meth)-acrylic type.
The copolymerization of one or more of these macromonomer(s) with one or more unsaturated ethylene comonomer(s) mentioned above in the description of the anchoring sequence, namely one or more compounds a), one or more neutral unsaturated ethylene monomer(s), and at least one macromonomer of hydrophobic character described hereinabove (from the primers usually used, for example organic peroxides, redox systems, or preferably azo compounds), will lead to the formation of a bigrafted copolymer according to the invention.
These grafts of hydrophilic character may also be fixed by grafting on a straight or branched copolymer constituted by one or more unsaturated ethylene monomer(s) mentioned above in the description of the anchoring sequence, namely one or more nitrogenous unsaturated ethylene monomer(s) a) and/or one or more reactive unsaturated ethylene monomer(s) used for grafting the compounds b) on the copolymer and/or one or more neutral unsaturated ethylene monomer(s) and/or one or more macromonomer(s) of hydrophobic character described hereinabove and/or hydrophilic, from one or more telomer(s) of hydrophilic character.
These telomers are constituted by a hydrosoluble polymer functionalized at the end of chain by a group containing a reactive hydrogen atom, xe2x80x94OH, xe2x80x94NH2, xe2x80x94NHR (where R is an alkyl radical comprising from 1 to 3 carbon atoms), xe2x80x94COOH, xe2x80x94SH.
The telomers may be grafted directly on the copolymer from reactive groups.
According to the invention, the monomer units constituting the macromonomers and telomers, used for preparing the sequence(s) of hydrophilic character will be selected for example from:
ethylene oxide,
(meth)acrylic acids, maleic acid, fumaric acid, itaconic acid,
derivatives of acrylamide such as (meth)acrylamide, N-methylacrylamide, N-isopropylacrylamide,
ethyleneimine,
vinyl alcohol,
vinylpyrrolidone, vinylmethyloxazolidone,
vinylsulfonate,
sodium methallylsulfonate,
glycerol methacrylate.
The grafted copolymers according to the invention are preferably prepared by radical method (xe2x80x9cmacromonomerxe2x80x9d technique, from macromonomers such as: poly(ethylene glycol) (meth)acrylates, the products HEMA-5 and HEMA-10 marketed by Bimax Chemicals Ltd. The molar mass of the grafts of hydrophilic character is chosen between 250 and 10000 and preferably between 300 and 3000.
On the other hand, the mass content represented by these hydrosoluble grafts in the final copolymer is from 10 to 90% and in particular from 15 to 70%.
In a subsequent aspect, the invention also concerns a process for preparing the grafted copolymers according to the invention.
As mentioned above, said copolymers may be prepared by radical copolymerization from macromonomers and/or by grafting polymers functionalized on a preformed chain, and consequently present a well controlled structure.
This mode of synthesis offers the further possibility of adjusting the molar mass of the anchoring sequence in order to increase the rate of adsorption of the copolymers on the particles, both inorganic and organic, as well as that of the side chains, improving their compatibility with the continuous phase.
Thus, by using the grafted copolymers according to the invention for preparing pigmentary concentrates, a state of dispersion superior to that obtained from the dispersants of the prior art is attained. Moreover, the high molar mass of the products according to the invention makes it possible to prepare pigmentary concentrates without elongation resin.
Radical-like copolymerization is preferably effected at a temperature included between 50xc2x0 C. and 140xc2x0 C., and the grafting reaction at a temperature preferably included between 20xc2x0 C. and 150xc2x0 C.
The order of addition of the monomers during radical copolymerization is advantageously as follows:
the macromonomers, of high molar mass and consequently less reactive, are incorporated with the solvent in the reactor from the beginning;
the comonomer(s) constituting the principal chain, which are more reactive, are continuously introduced in the course of time, so that their concentration is always low with respect to that of the macromonomers.
According to a first variant, the invention therefore concerns a process for preparing a grafted copolymer as defined hereinabove comprising at least three sequences of distinct chemical nature, among which a sequence of anchoring on the solid particles, one or more sequence(s) of hydrophobic character and one or more sequence(s) of hydrophilic character, in which the principal chain is a sequence of anchoring on the solid particles, characterized in that the following is effected:
1) the radical copolymerization of:
i) 0 to 80% by mass, preferably 0 to 40% by mass, of one or more monomer(s) comprising at least one basic nitrogenous group of the heterocyclic type, xe2x80x94NH2, xe2x80x94NHR, NR2, xe2x80x94CONH2, xe2x80x94CONHR, xe2x80x94CONR2 (where R is an alkyl radical (C1-C6), optionally substituted by one or more group(s) xe2x80x94COOxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94 xe2x80x94OHxe2x80x94, xe2x80x94SO3H) and
ii) 0 to 90% by mass, preferably 0 to 80% by mass, of one or more macromonomer(s) represented by the formula: 
where R4, R5, R6, identical or different, represent an atom of hydrogen or an alkyl radical (C1-C4),
R7 is a sequence of hydrophobic character, constituted by a straight or branched hydrocarbon chain, cycloalkyl or aromatic, which may comprise groups xe2x80x94COOxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94Fxe2x80x94, xe2x80x94Si(ORxe2x80x2)n(Rxe2x80x3)2-nxe2x80x94 (where Rxe2x80x2 and Rxe2x80x3 represent similar or different alkyl or aryl radicals (C1-C10), and n=0 to 2) formed by monomer units of which the parameter of solubility is less than or equal to 21.5 Jxc2xd/cm{fraction (3/2)}, preferably less than 19 Jxc2xd/cm{fraction (3/2)}, and whose molar mass is included between 250 and 10000, preferably between 500 and 3500, and
iii) 0 to 90% by mass, preferably 0 to 70% by mass, of one or more macromonomer(s) represented by the formula: 
where R4, R5, R6 are as defined hereinabove, and
R8 is a sequence of hydrophilic character, constituted by a straight or branched hydrocarbon chain comprising groups xe2x80x94Oxe2x80x94, xe2x80x94OHxe2x80x94, NCOxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94COOH, xe2x80x94CONH2, xe2x80x94CONHRxe2x80x2xe2x80x3 (where Rxe2x80x2xe2x80x3 is an alkyl radical (C1-C3), xe2x80x94NHxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO3H, formed by monomer units of which the parameter of solubility is greater than 22 Jxc2xd/cm{fraction (3/2)}, preferably greater than 22.5 Jxc2xd/cm{fraction (3/2)}, and of which the molar mass is included between 250 and 10000, preferably between 300 and 3000, and
iv) 0 to 80% by mass, preferably 0 to 40%, of one or more monomer(s) containing at least one group capable of being engaged in a coupling reaction, and
v) 0 to 76% by mass, preferably 0 to 28%, of one or more unsaturated ethylene monomer(s) which may contain up to 25 carbon atoms, apart from the monomers already mentioned in i), it being understood that, if one of the mass contents of the compounds defined in i), ii) and/or iii) is zero, the mass content of the compounds defined in iv) is different from 0, and
2) grafting on this preformed chain of:
vi) 0 to 80% by mass, preferably 0 to 40%, of one or more molecule(s) deriving from a compound comprising at least one heterocyclic basic nitrogenous group, xe2x80x94NH2, xe2x80x94NHR or xe2x80x94NR2 (where R is an alkyl radical (C1-C6) and containing at least one group capable of being engaged in a coupling reaction, and
vii) 0 to 90% by mass, preferably 0 to 80% by mass, of one or more telomer(s) represented by the formula:
Gxe2x80x94R7
where G represents a group containing a reactive hydrogen atom, xe2x80x94OH, xe2x80x94COOH, xe2x80x94SHxe2x80x94, xe2x80x94NH2, xe2x80x94NHRxe2x80x2xe2x80x3 (where Rxe2x80x3 is an alkyl radical (C1-C3)), and R7 is as defined hereinabove, and
viii) 0 to 90% by mass, preferably 0 to 70%, of one or more telomer(s) represented by the formula
Gxe2x80x94R8
where G and R8 are as defined hereinabove, it being understood that:
the contents by mass of the compounds defined in i) and in vi) cannot be equal to 0 simultaneously, and when one of them is equal to 0, then the other is equal to at least 1%,
the contents by mass of the compounds defined in ii) and in vii) cannot be equal to 0 simultaneously, and when one of them is equal to 0, then the other is equal to at least 10%,
the contents by mass of the compounds defined in iii) and in viii) cannot be equal to 0 simultaneously, and when one of them is equal to 0, then the other is equal to at least 10%.
According to this first variant of the process, a grafted copolymer as defined above is prepared, constituted by a principal chain for anchoring on the solid particles and at least 2 grafts, respectively hydrophobic and hydrophilic, said copolymers being preferred products according to the invention.
According to a second variant, the invention also concerns a process for preparing a grafted copolymer comprising at least three sequences of distinct chemical nature, among which one or more anchoring sequence(s), a sequence of hydrophobic character and one or more sequence(s) of hydrophilic character, in which the principal chain is a sequence of hydrophobic character, as defined hereinabove,
characterized in that the radical copolymerization is effected of:
i) 10 to 90% by mass, preferably 25 to 80% by mass, of one or more monomer(s) of hydrophobic character comprising at least one aromatic group, xe2x80x94COOxe2x80x94, xe2x80x94F, or xe2x80x94Si(ORxe2x80x2) n (Rxe2x80x3)2xe2x80x94 (where Rxe2x80x2 and Rxe2x80x3 represent identical or different alkyl or aryl radicals (C1-C10), and n=0 to 2) constituting after polymerization a chain formed by monomer units of which the parameter of solubility is less than or equal to 21.5 Jxc2xd/cm{fraction (3/2)}, preferably less than 19 Jxc2xd/cm{fraction (3/2)}, and of which the molar mass is included between 250 and 10000, preferably between 500 and 3500, and
ii) 0 to 90% by mass, preferably 0 to 70% by mass, of one or more macromonomer(s) represented by the formula: 
where R4, R5, R6 are as defined hereinabove, and
R8 is a sequence of hydrophilic character, constituted by a straight or branched hydrocarbon chain, comprising groups xe2x80x94Oxe2x80x94, xe2x80x94OH, xe2x80x94NCOxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94COOH, xe2x80x94CONH2, xe2x80x94CONHRxe2x80x3xe2x80x2 (where Rxe2x80x3xe2x80x2 is an alkyl radical (C1-C3)), xe2x80x94NHxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO3H, formed by monomer units of which the parameter of solubility is greater than 22 Jxc2xd/cm{fraction (3/2)}, preferably greater than 22.5 Jxc2xd/cm{fraction (3/2)} and of which the molar mass is included between 250 and 10000, preferably between 300 and 3000, and
iii) 0 to 80% by mass, preferably 0 to 40% by mass, of one or more macromonomer(s) represented by the formula 
where R4, R5, R6 are as defined hereinabove, and
R9 is an anchoring sequence, constituted by a straight or branched hydrocarbon chain, cycloalkyl or aromatic, comprising basic 20 nitrogenous groups of type: heterocyclic, xe2x80x94NH2, xe2x80x94NHxe2x80x94, xe2x80x94NHR, xe2x80x94NR2, CONH2, CONHR, xe2x80x94CONR2 (where R is an alkyl radical (C1-C6), optionally substituted by one or more groups xe2x80x94OH, xe2x80x94COOxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94SO3H) which may comprise groups xe2x80x94COOxe2x80x94 and of which the molar mass is included between 150 and 10000, preferably between 300 and 3000, the content of basic nitrogenous monomers in the anchoring chain by mass being 5% minimum and preferably 30%, and
iv) 0 to 80% by mass, preferably 0 to 40%, of one or more monomer(s) containing at least one group capable of being engaged in a coupling reaction,
it being understood that if one of the contents by mass of the compounds defined in i), ii) and/or iii) is zero, the content by mass of the compounds defined in iv) is different from 0, and
2) grafting on this preformed chain of:
v) 0 to 90% by mass, preferably 0 to 70%, of one or more telomer(s) represented by the formula
Gxe2x80x94R8
where G represents a group containing an atom of reactive hydrogen, xe2x80x94OH, xe2x80x94COOH, xe2x80x94SH, xe2x80x94NH2, xe2x80x94NHRxe2x80x2xe2x80x3 (where Rxe2x80x2xe2x80x3 is an alkyl radical (C1-C3)), and R8 is as defined hereinabove, and
vi) 0 to 80% by mass, preferably 0 to 40%, of one or more telomer(s) represented by the formula
Gxe2x80x94R9
where G and R9 are as defined hereinabove, it being understood that:
the contents by mass of the compounds defined in ii) and in
v) cannot be equal to 0 simultaneously, and when one of them is equal to 0, then the other is equal to at least 10%,
the contents by mass of the compounds defined in iii) and
vi) cannot be equal to 0 simultaneously and when one of them is equal to 0, then the other is equal to at least 1%.
According to this second variant of the process, a grafted copolymer as defined above is prepared, constituted by a principal hydrophobic chain and at least 2 respective hydrophilic and anchoring grafts.
According to a subsequent aspect, the invention relates to a third variant of the process for preparing a grafted copolymer comprising at least three sequences of distinct chemical nature, among which one or more anchoring sequence(s), one or more sequence(s) of hydrophobic character and a sequence of hydrophilic character as defined hereinabove, in which the principal chain is a sequence of hydrophilic character,
characterized in that the radical copolymerization is effected of
i) 10 to 90% by mass, preferably 15 to 70% by mass, of one or more monomer(s) of hydrophilic character comprising at least one group selected from xe2x80x94Oxe2x80x94, xe2x80x94OHxe2x80x94, xe2x80x94COOHxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94SO3H, xe2x80x94CONH2, xe2x80x94CONHRxe2x80x2xe2x80x3 (where Rxe2x80x2xe2x80x3 is an alkyl radical (C1-C3)) and constituting after polymerization a chain formed by monomer units of which the parameter of solubility is greater than 22 Jxc2xd/cm{fraction (3/2)}, preferably greater than 22.5 Jxc2xd/cm{fraction (3/2)}, and whose molar mass is included between 250 and 10000, preferably between 300 and 3000, and
ii) 0 to 90% by mass, preferably 0 to 80% by mass, of one or more macromonomer(s) represented by the formula: 
where R4, R5, R6, identical or different, represent an atom of hydrogen or an alkyl radical (C1-C4),
R7 is a sequence of hydrophobic character, constituted by a straight or branched hydrocarbon chain, cycloalkyl or aromatic, able to comprise groups xe2x80x94COOxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94F, xe2x80x94Si(ORxe2x80x2)n(Rxe2x80x3)2-nxe2x80x94 (where Rxe2x80x2 and Rxe2x80x3 represent identical or different alkyl or aryl radicals (C1-C10), and n=0 to 2), formed by monomer units of which the parameter of solubility is less than or equal to 21.5 Jxc2xd/cm{fraction (3/2)}, preferably less than 19 Jxc2xd/cm{fraction (3/2)} and whose molar mass is included between 250 and 10000, preferably between 500 and 3500 and
iii) 0 to 80% by mass, preferably 0 to 40% by mass, of one or more macromonomer(s) represented by the formula: 
where R4, R5, R6 are as defined hereinabove, and
R9 is an anchoring sequence constituted by a straight or branched hydrocarbon chain, cycloalkyl or aromatic, comprising basic nitrogenous groups of type: heterocyclic, xe2x80x94NH2, xe2x80x94NHxe2x80x94, xe2x80x94NHR, xe2x80x94NR2, xe2x80x94CONH2, xe2x80x94CONHR, xe2x80x94CONR2 (where R is an alkyl radical (C1-C6), optionally substituted by one or more groups xe2x80x94OH, xe2x80x94COOxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94SO3H) which may comprise xe2x80x94COOxe2x80x94 groups and of which the molar mass is included between 150 and 10000, preferably between 300 and 3000, the content of basic nitrogenous monomers in the anchoring chain by mass being 5% minimum and preferably 30%, and
iv) 0 to 80% by mass, preferably 0 to 40%, of one or more monomer(s) containing at least one group capable of being engaged in a coupling reaction,
it being understood that, if one of the contents by mass of the compounds defined in i), ii) and/or iii) is zero, the content by mass of the compounds defined in iv) is different from 0, and
2) grafting on this preformed chain of
v) 0 to 90% by mass, preferably 0 to 80% by mass, of one or more telomer(s) represented by the formula:
Gxe2x80x94R7
where G represents a group containing an atom of reactive hydrogen, xe2x80x94OH, xe2x80x94COOH, xe2x80x94SH, xe2x80x94NH2, xe2x80x94NHRxe2x80x3 (where Rxe2x80x2xe2x80x3 is an alkyl radical (C1-C3)) and R7 is as defined hereinabove, and
vi) 0 to 80% by mass, preferably 0 to 40%, of one or more telomer(s) represented by the formula
Gxe2x80x94R9
where G and R9 are as defined hereinabove, it being understood that:
the contents by mass of the compounds defined in ii) and in
v) cannot be equal to 0 simultaneously and when one of them is equal to 0, then the other is equal to at least 10%,
the contents by mass of the compounds defined in iii) and in vi) cannot be equal to 0 simultaneously and when one of them is equal to 0, then the other is equal to at least 1%.
According to this third variant of the process, a grafted copolymer as defined hereinabove is prepared, constituted by a principal hydrophilic chain and at least 2 respective hydrophobic and anchoring grafts.
Preferred grafted copolymers according to the invention are those comprising
a principal chain for anchoring on the solid particles comprising dialkylaminoethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, N,N-dimethylacrylamide groups, alone or mixed,
one or more hydrophilic grafts poly(ethylene oxide), and
one or more hydrophobic grafts based on alkyl (meth)acrylate, vinyl esters alone or copolymerized with styrene and alkylstyrene derivatives, fluorinated monomers (trifluoroethyl methacrylate), or 3-(trimethoxysilyl)propyl methacrylate.
The grafted copolymers according to the invention are advantageously usable for the preparation of pigmentary concentrates. In fact, the presence within the copolymer of sequences of hydrophilic and hydrophobic character allows the dispersion of a number of solid particles in a liquid and the formulation of pigmentary pastes of equal performances in an aqueous and/or organic medium.
Said copolymers also advantageously allow the preparation of pigmentary concentrates without added resin, which improves the compatibility of these pastes with a large range of binding agents.
By way of example, pigmentary concentrates containing the copolymers according to the invention may be prepared by using the following pigments, fillers and fibrous solids:
inorganic pigments such as titanium dioxides, zinc oxides, zinc sulfates, zinc phosphates, lithopones, carbon blacks, iron oxides, manganese phosphates, cobalt aluminates, antimony sulfates or zinc chromates,
metallic pigments,
organic pigments such as oxazines, dioxazines, thiazines, phthalocyanines, xanthenes, acrydines, quinacridones or perylenes.
The grafted copolyers according to the invention will advantageously be used for incorporating fillers or fibrous solids in paints, particularly for the dispersion of aluminum oxides and hydroxides, quartz, silicas, talcs, kaolins, micas, calcium sulfates, barium sulfates or calcium carbonates. The paint films made by using said copolymers advantageously present a reduced sensitivity to water, while conserving a high brilliancy at application.
In order to prepare pigmentary concentrates, the grafted copolymers according to the invention will preferably be used at a rate of a solid particle/dispersant mass ratio included between 1/50 and 100/1, in particular 1/10 and 20/1.
The reactional mixture obtained at the end of the synthesis of the grafted copolyer may be used either directly or after concentration by distillation under reduced pressure or azeotropic distillation possibly by adding a cosolvent.
The reaction medium may also be replaced by adding a solvent having a higher boiling temperature or forming an azeotrope therewith, then eliminating the reaction solvent by distillation under reduced pressure or azeotropic distillation. The reaction solvent may thus advantageously be replaced by water or a liquid miscible with water to formulate aqueous pastes.
Alternately, it is possible to isolate the grafted copolymer according to the invention in a selective solvent or by complete elimination of the reaction solvent. Said copolymer will then be redissolved in an adequate liquid or used as such if its viscosity allows this.
The pigments, fillers and fibrous solids may also be treated by a solution of grafted copolymer according to the invention, for example in fluidized bed or in a cyclone, the coated particles thus obtained then being redispersed in a liquid or a mixture of appropriate liquids.
The dispersions of solid particles, pigments, fillers or fibrous solids in a liquid are effected in accordance with the grinding and impasting processes usual in the domain of paints and inks.